Vehicle suspensions have commonly used heavy beams or beams and leaf spring assemblies to resiliently support the axle relative to the frame and to carry loads on the axle fore and aft to frame-mounted supporting devices. The same beams or beams mad spring assemblies also are used to control the amount of roll a vehicle experiences when the vehicle, for example, travels around a corner. Thus, the same assembly is used to provide both a beam function and a roll springing function. As a result, conventional assemblies are very heavy and require strong components that must withstand large loads.
These assemblies are pivotally connected at one end to a bracket rigidly mounted on the frame of the vehicle in a manner such that they rotate about a fixed pivot relative to the frame when the axle moves vertically. However, the vertical movement of the axle is caused by rocking of the axle about a longitudinal fore and aft axis as the wheels on opposite sides of the vehicle go up and down over irregularities in the road surface such that the ends of the axle also move laterally, relative to the frame along a transverse axis. As a result, the connection between an axle of the suspension and the beams or the leaf spring of the suspension to the frame requires several connection components that must be made with very heavy-duty, strong material to withstand large lateral and twisting or torque loads caused by the rocking of the axle. The connection components attached to the beam, such as a spring steel beam, or to the beam and spring combination create "dead" areas of the spring portions, thereby resulting in heavy spring portions that are not fully utilized. In addition, the beams and leaf springs must also be made of heavy-duty, strong material to withstand the large lateral and torque loads. As a result, the convention suspensions are very complex and heavy.
Particularly in large bulk carrying vehicles, such as those which carry sand, gravel, or other heavy payloads, the increased weight required to make the suspension strong enough to withstand the large lateral and torque loads caused by the axle being raised at one end results in excess weight of the vehicle, thereby reducing the maximum payload for the vehicle.